Yazar "Togrul, Mahmut" seçeneğine göre listele

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    Amide-based tripodal receptors for selective anion recognition
    (Springer, 2010) Ozturk, Gulsen; Colak, Mehmet; Togrul, Mahmut
    In order to improve efficiency and reduce waste production; the microwaves offer mild methods to prepare amides based neutral tripodals receptors directly from non activated carboxylic acids and amines in the absences of coupling reagents and solvents, with high yield and very short time. The preliminary 1H NMR titration experiments revealed that tripodals receptor 1 and 2 can recognize H2PO4 (-) and C6H5CO2 (-) through a 1:1 binding-stoichiometry in preference over other anions (PF6 (-), ClO4 (-), HSO4 (-) and Br-). The tripodal receptor 2 showed higher binding to the all examined anions than the tripodal receptor 1.
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    Asymmetric transfer hydrogenation of acetophenone derivatives with novel chiral phosphinite based ?6-p-cymene/ruthenium(II) catalysts
    (Elsevier Science Sa, 2011) Aydemir, Murat; Meric, Nermin; Baysal, Akin; Turgut, Yilmaz; Kayan, Cezmi; Seker, Sevil; Togrul, Mahmut
    Enantioselective reduction of prochiral ketones to optically active secondary alcohols is an important subject in synthetic organic chemistry because the resulting chiral alcohols are extremely useful, biologically active compounds. The new chiral ligands (2R)-2-[benzyl{(2-((diphenylphosphanyl)oxy)ethyl)}amino]butyldiphenylphosphinite, 1 and (2R)-2-[benzyl{(2-((dicyclohexylphosphanyl)oxy)ethyl)}amino]butyldicyclohexylphosphinite, 2 and the corresponding ruthenium(II) complexes 3 and 4 have been prepared. The structures of these complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. P-31-{H-1} NMR, DEPT, H-1-C-13 HETCOR or H-1-H-1 COSY correlation experiments were used to confirm the spectral assignments. These ruthenium(II) ephosphinite complexes have been used as catalysts for the asymmetric transfer hydrogenation of acetophenone derivatives. Under optimized conditions, aromatic ketones were reduced in good conversions and in moderate to good enantioselectivities (up to 85% ee). (C) 2011 Elsevier B. V. All rights reserved.
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    Asymmetric transfer hydrogenation of aromatic ketones with the ruthenium(II) catalyst derived from C2 symmetric N,N?-bis[(1S)-1-benzyl-2-O-(diphenylphosphinite)ethyl]ethanediamide
    (Elsevier Science Sa, 2010) Aydemir, Murat; Meric, Nermin; Durap, Feyyaz; Baysal, Akin; Togrul, Mahmut
    Asymmetric transfer hydrogenation of ketones with chiral molecular catalysts is realized to be one of the most magnificent tools to access chiral alcohols in organic synthesis. A new chiral phosphinite compound N,N'-bis[(1S)-1-benzyl-2-O-(diphenylphosphinite)ethyl]ethanediamide (1), has been synthesized by the reaction of chlorodiphenylphosphine with N,N'-bis[(1S)-1-benzyl-2-hydroxyethyl]ethanediamide under argon atmosphere. The oxidation of 1 with aqueous hydrogen peroxide, elemental sulfur or grey selenium in toluene gave the corresponding oxide 1a, sulfide 1b and selenide 1c, respectively. Pd, Pt and Ru complexes were obtained by the reaction of 1 with [MCl2(cod)] (M: Pd 1d, Pt 1e) and [Ru(p-cymene)Cl-2](2) 1f, respectively. All these new complexes were characterized by using NMR, FT-IR spectroscopies and microanalysis. Additionally, as a demonstration of their catalytic reactivity, the ruthenium complex 1f was tested as catalyst in the asymmetric transfer hydrogenation reactions of acetophenone derivatives with iPrOH was also investigated. (C) 2010 Elsevier B.V. All rights reserved.
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    The enantiomeric recognition of chiral organic ammonium salts by chiral pyridino-macrocycles bearing aminoalcohol subunits
    (Pergamon-Elsevier Science Ltd, 2009) Ozer, Hayriye; Kocakaya, Safak Ozhan; Akgun, Abuzer; Hosgoren, Halil; Togrul, Mahmut
    Pyridine-based macrocycles were prepared by treating 2,6-bis[[2'6'-bis(bromomethyl)-4'-methylphenoxy]methyl]pyridine 3 with the appropriate chiral aminoalcohols. The enantiomeric recognition of these macrocycles bearing aminoalcohol subunits of the pyridinocrown type ligand was evaluated for chiral organic ammonium salts by UV titration. The important differences were observed in the K-a values of (R)-Am2 and (S)-Am2 for (S,S,S)-1, (S,SS)-2 and (S,S,S)-3 hosts, K-S/K-R = 5.0, K-S/K-R = 2.4 and K-S/K-R = 5.0. respectively. There seems to be a general tendency for hosts to recognise (S)-enantiomers for both Am1 and Am2. (C) 2009 Elsevier Ltd. All rights reserved.
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    A facile synthesis of amide-based receptors under microwave conditions: investigation of their anion recognition properties by experimental and computational tools
    (Springer, 2017) Ozturk, Gulsen; Subari, Salih; Seker, Sevil; Togrul, Mahmut; Kocakay, Safak Ozhan; Ercan, Selami; Pirinccioglu, Necmettin
    Two novel amide-based receptors were synthesized under microwave irradiation. Their chemical structures were confirmed by IR, H-1 NMR, C-13 NMR, and elemental analysis. The binding properties of these amide-based receptors to various anions (H2PO4-, HSO4-, C6H5CO2-, CH3CO2-, ClO4-, F-, Cl-, and Br-) were examined by UV titration in THF at 20 degrees C. The results indicated that the receptors form 1: 1 complexes with anions and they have the strongest affinity for fluoride (F-) among the anions considered. Molecular dynamics calculations by AMBER and quantum mechanical calculations performed at the B3LYP and M062X levels of theory using the 6-31 + g(d,p) basis set provided models for the complexation mode between the receptors and anions and yielded binding energies for the complexes.
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    Microwave-assisted synthesis of novel amide based chiral tripodal receptors for recognition of cation and anion sensors
    (Arkat Usa Inc, 2016) Azizoglu, Sevil S.; Kaplan, Seref; Ozturk, Gulsen; Turgut, Yilmaz; Togrul, Mahmut
    Five novel amide based chiral tripodal receptors were synthesized under microwave irradiation by reacting nitrilotriacetic acid with chiral amino alcohols in a solvent-free medium with high yields (>= 90%). The recognition affinities of these tripodal receptors were investigated towards anions and chiral organic ammonium cations using H-1 NMR titration method. The results show that receptor 1 displays more affinity against anions compared with other receptors and the tripodal receptor 4 demonstrated a significant enantiomeric selectivity towards the (R)-naphthylethylammonium perchlorate (ERF 54%).
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    A modular design of ruthenium(II) catalysts with chiral C2-symmetric phosphinite ligands for effective asymmetric transfer hydrogenation of aromatic ketones
    (Pergamon-Elsevier Science Ltd, 2010) Aydemir, Murat; Meric, Nermin; Baysal, Akin; Gumgum, Bahattin; Togrul, Mahmut; Turgut, Yilmaz
    Hydrogen-transfer reduction processes are attracting increasing interest from synthetic chemists in view of their operational simplicity. The new chiral C-2-symmetric ligands N,N'-bis-[(1S)-1-sec-butyl-2-O-(diphenylphosphinite)ethyl]ethanediamide, 1 and N,N'-bis-[(1S)-1-phenyl-2-O-(diphenylphosphinite)ethyl]ethanediamide, 2 and the corresponding ruthenium complexes 3 and 4 have been prepared and their structures have been elucidated by a combination of multi-nuclear NMR spectroscopy, IR spectroscopy, and elemental analysis. H-1-P-31 NMR, DEPT, H-1-C-13 HETCOR, or H-1-H-1 COSY correlation experiments were used to confirm the spectral assignments. The catalytic activity of complexes 3 and 4 in transfer hydrogenation of acetophenone derivatives by iso-PrOH has also been studied. Under optimized conditions, these chiral ruthenium complexes serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iso-PrOH and act as excellent catalysts, giving the corresponding chiral alcohols in 99% yield and up to 75% ee. This transfer hydrogenation is characterized by low reversibility under these conditions. (C) 2010 Elsevier Ltd. All rights reserved.
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    Novel C2-symmetric macrocycles bearing diamide-diester groups
    (Amer Chemical Soc, 2008) Sunkur, Murat; Baris, Deniz; Hosgoren, Halil; Togrul, Mahmut
    We synthesized a series of novel macrocycles with diamide-diester groups (S,S)-1, (S,S)-2, (S,S)-3, and (R,R)-1, derived from dimethyloxalate and amino alcohols by high dilution technique, and evaluated enantiomeric recognition properties of these macrocycles toward primary alkyl ammonium salts by H-1 NMR titration. Taking into account the host employed, important differences were observed in the K-a values of (R)-Am and (S)-Am for (S,S)-1 and (R,R)-1 hosts, K-S/K-R = 5.55 and K-R/K-S = 3.65, Delta Delta G(o) = 0.43 and -0.32 kJ mol(-1), respectively. There seems a general tendency for the host to include the guests with the same absolute configuration.
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    Pyridine containing chiral macrocycles: synthesis and their enantiomeric recognition for amino acid derivatives
    (Pergamon-Elsevier Science Ltd, 2011) Deniz, Pinar; Turgut, Yilmaz; Togrul, Mahmut; Hosgoren, Halil
    Four novel C(2)-symmetric enantiomerically pure, chiral pyridine-18-crown-6 type macrocycles containing lipophilic chains at the stereogenic centers were prepared. The enantioselectivity of the new ligands toward the enantiomers of D-,L-amino acid methyl ester derivatives were also determined by (1)H NMR titration method. These novel macrocycles have been showed to be strong complexing agents for D- and L-amino acid methyl ester hydrochloride salts (with K(ass) up to 13590 M(-1) and Delta G(0) up to 23.3 kJ mol(-1) and selectivity ratio: 80:20) by (1)H NMR titration methods. These macrocyclic hosts exhibited enantioselective binding towards the D-enantiomer of valine methyl ester hydrochloride with K(D)/K(L), up to 5.08 in CDCl(3) with 0.25% CD(3)OD. (C) 2011 Elsevier Ltd. All rights reserved.
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    Synthesis of bis(amino alcohol)oxalamides and their usage for the preconcentration of trace metals by cloud point extraction
    (Japan Soc Analytical Chemistry, 2008) Kilinc, Ersin; Cetin, Adnan; Togrul, Mahmut; Hosgoren, Halif
    C-2-Symmetric two bis(amino, alcohol)oxalamides (diamidediols) were synthesized and fully characterized. A new method was developed and successfully applied for the simultaneous preconcentration of both trace and toxic metals in water, by using C-2-symmetric compounds. Under the optimum experimental conditions (i.e. pH = 10.0 +/- 0.2, 2.75 x 10(-3) mol L-1 N,N'-bis[(IR)-1-ethyl-2-hydroxyethyl]ethanediamide (DAD1), 1.75 x 10(-3) mol L-1 N,N'-bis[(1S)-1-benzyl-2-hydroxyethyl]ethanediamide (DAD2), 0 10% w/v octylphenoxy-polyethoxyethanol (Triton X-114)), calibration graphs were linear in the range of 2.5 - 25.0 ng mL(-1) for Cu and Cd, 5.0 - 25.0 ng mL(-1) for Co and Ni. The enrichment factors were 18, 23, 18 and 20 for Cd, Cu, Co and Ni in the case of DAD I, respectively; 20, 22, 17 and 20 for Cd, Cu, Co and Ni in the case of DAD2. The limits of detection for DAD1 were found to be 0.45, 0.50, 1.25 and 0.60 ng mL(-1) for Cd, Cu, Co and Ni, respectively, and for DAD2 were found to be 0.44, 0.25, 0.60 and 1.55 ng mL(-1) for Cd, Cu, Co and Ni, respectively. The developed method was applied to the determination of Cu, Cd, Co and Ni in water samples and certified reference materials with satisfactory results.
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    Synthesis of rigid and C2-symmetric 18-crown-6 type macrocycles bearing diamide-diester groups: enantiomeric recognition for ?-(1-naphthyl) ethylammonium perchlorate salts
    (Pergamon-Elsevier Science Ltd, 2010) Baris, Deniz; Seker, Sevil; Hosgoren, Halil; Togrul, Mahmut
    A series of rigid and chiral C-2-symmetric 18-crown-6 type macrocycles (S,S)-4, (S,S)-5, (S,S)-6 and (R,R)-2 bearing diamide-ester groups were synthesized. The binding properties of these macrocycles were examined for ot-(1-naphthypethylammonium perchlorates salts by an 1H NMR titration method. Taking into account the host employed, important differences were observed in the Ka values of (R)- and (S)-enantiomers of guests for macrocycles (S,S)-4 and (S,S)-6, Ks/KR = 3.6, and Ks/KR = 0.1 (KR/Ks = 10.3).6.,6,G= 3.19 and Delta Delta G= -5.77 kJ mol(-1), respectively. The results indicated excellent enantioselectivity of macrocyclic (S,S)-6 towards the enantiomers of alpha-(1-naphthyl)ethylammonium perchlorate salts. (C) 2010 Elsevier Ltd. All rights reserved.
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    Synthesis of rigid and C2-symmetric pyridino-15-crown-5 type macrocycles bearing diamide-diester functions: enantiomeric recognition for chiral primary organoammonium perchlorate salts
    (Pergamon-Elsevier Science Ltd, 2014) Seker, Sevil; Baris, Deniz; Arslan, Nevin; Turgut, Yilmaz; Pirinccioglu, Necmettin; Togrul, Mahmut
    Four novel C-2-symmetric macrocyclic compounds with a pyridine function and possessing amide and ester lingeages were prepared. The enantiomeric discrimination abilities of these macrocycles against alpha-phenylethylammonium and alpha-(1-naphthyl)ethylammonium perchlorate salts were measured by standard H-1 NMR titration techniques in DMSO-d(6). A binding constant ratio of 31 (Kbind(S)/Kbind(R)) for two enantiomers of alpha-(1-naphthyl)ethylammonium salt with the macrocyclic host (S,S)-4 bearing phenyl arms was observed, which corresponds to an enantiomeric discrimination of approximately 94%. Molecular dynamic calculations were performed for some of the supramolecular complexes to in order to gain insight into the mode of molecular recognition between the macrocyclic compounds and ammonium salts; these results were consistent with experimental observations, which may be relevant to those in biochemical processes occurring in organisms. (C) 2014 Elsevier Ltd. All rights reserved.